U.S. patent number 4,320,291 [Application Number 06/099,823] was granted by the patent office on 1982-03-16 for optical instrument.
This patent grant is currently assigned to Yuasa Battery Company Limited. Invention is credited to Hiromu Uramoto.
United States Patent |
4,320,291 |
Uramoto |
March 16, 1982 |
Optical instrument
Abstract
An optical instrument for measuring the specific gravity of a
solution, particularly the specific gravity of the acid in a lead
acid battery, which incudes a base part and a transparent member,
the transparent member including an incident light surface and
reflector. The instrument further includes a light source arranged
in the base part of the transparent member which is capable of
radiating a straight-lined ray into the transparent member parallel
to the axis of the member, and a photosensitive element for
receiving light reflected by the incident light surface and the
reflector. During use the instrument is positioned such that the
transparent member is in contact with the solution whose specific
gravity is to be measured.
Inventors: |
Uramoto; Hiromu (Takatsuki,
JP) |
Assignee: |
Yuasa Battery Company Limited
(Takatsuki, JP)
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Family
ID: |
14939888 |
Appl.
No.: |
06/099,823 |
Filed: |
December 3, 1979 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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967985 |
Dec 11, 1978 |
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804298 |
Jun 1, 1977 |
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Foreign Application Priority Data
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Oct 20, 1976 [JP] |
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51-126628 |
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Current U.S.
Class: |
250/227.11;
356/136; 429/92; 250/903; 429/91 |
Current CPC
Class: |
G01N
21/431 (20130101); Y10S 250/903 (20130101) |
Current International
Class: |
G01N
21/41 (20060101); G01N 21/43 (20060101); G02B
005/14 () |
Field of
Search: |
;250/227,577
;356/135,136,137 ;73/293 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nelms; David C.
Attorney, Agent or Firm: Watson, Cole, Grindle &
Watson
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIIONS
This application is a continuation-in-part application of
application Ser. No. 967,985 filed Dec. 11, 1978, now abandoned,
which in turn was a continuation-in-part application of application
Ser. No. 804,298, filed June 1, 1977, now abandoned.
Claims
I claim:
1. An optical instrument for measuring the specific gravity of a
solution, said instrument comprising
an elongated base body having a first end and a second end,
a light-emitting means located near said first end of the elongated
base body for emitting a ray of non-divergent light through the
elongated base body,
a photosensitive element located near said first end of the
elongated base body for sensing light passing through the elongated
base body in parallel with said ray of nondivergent light emitted
by said light-emitting means, and
a transparent glass member having a refractive index value of not
less than 1.5 sealingly connected to said second end of the
elongated base body, said glass member including only two
light-contacting surfaces which consist of (a) an incident light
surface which is positioned and inclined such that said ray of
non-divergent light emitted from said light-emitting means will
strike the incident light surface and be divided into a light
portion entering the solution in which the optical instrument is
partly immersed and a reflected portion, and (b) a reflector
surface; said reflector surface including a reflective coating
enabling 100% of the light hitting said reflector surface to be
redirected towards said photosensitive element in a direction
parallel to the ray of non-divergent light emitted from said
light-emitting means.
2. The optical instrument as claimed in claim 1, wherein said
elongated base member includes two parallel passageways
therethrough, one for the passage of said ray of nondivergent light
emitted from said light-emittting means towards said incident light
surface and one for the passage of the light reflected from said
reflector surface towards said photosensitive element.
3. The optical instrument as claimed in claim 2, wherein a light
ray-limiting means is positioned in the passageway through which
the ray of non-divergent light from said light-emitting means
passes.
4. The optical instrument as claimed in claim 3, wherein said light
ray-limiting means comprises a focusing lens.
5. The optical instrument as claimed in claim 3, wherein said light
ray-limiting means comprises a tubular member.
6. The optical instrument as claimed in claim 3 wherein said light
ray-limiting means controls the divergence of the ray of light
passing therethrough such that it has an expansion angle of not
more than 1.5.degree., the optical instrument being thereby adapted
to measure a specific weight of about 1.000 to 1.320 of sulfuric
acid.
7. An optical instrument for measuring the specific gravity of a
solution, said instrument comprising
an elongated base body having a first end and a second end,
a light-emitting means located near said first end of the elongated
base body for emitting a ray of nondivergent light through the
elongated base body,
a photosensitive element located near said first end of the
elongated base body for sensing light passing through the elongated
base body in parallel with said ray of non-divergent light emitted
by said light-emitting means, and
a transparent glass member having a refractive index value of not
less than 1.5 sealingly connected to said second end of the
elongated base body, said glass member including only two
light-contacting surfaces which consist of (a) a reflector surface
which is positioned and inclined such that said ray of
non-divergent light emitted from said light-emitting means will
strike the reflector surface, and (b) an incident light surface
positioned such that the light reflected by said reflector surface
will strike the incident light surface and be divided into a light
portion entering the solution in which the optical instrument is
partly immersed and a reflected portion which is directed towards
said photosensitive element in parallel with the ray of
non-divergent light emitted from said lightemitting means; said
reflector surface including a reflective coating enabling 100% of
the light hitting said reflector surface to be redirected towards
said incident light surface.
8. The optical instrument as claimed in claim 7, wherein said
elongated base member includes two parallel passageways
therethrough, one for the passage of said ray of nondivergent light
emitted from said light-emitting means towards said reflector
surface and one for the passage of the light reflected from said
incident light surface towards said photosensitive element.
9. The optical instrument as claimed in claim 8, wherein a light
ray-limiting means is positioned in the passageway through which
the ray of non-divergent light from said lightemitting means
passes.
10. The optical instrument as claimed in claim 9, wherein said
light ray-limiting means comprises a focusing lens.
11. The optical instrument as claimed in claim 9, wherein said
light ray-limiting means comprises a tubular member.
12. The optical instrument as claimed in claim 8 wherein said light
ray-limiting means controls the divergence of the ray of light
passing therethrough such that it has an expansion angle of not
more than 1.5.degree., the optical instrument being thereby adapted
to measure a specific weight of about 1.000 to 1.320 of sulfuric
acid.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to optical instruments for measuring
the density of a solution.
2. Description of the Prior Art
Refractometers for measuring the refractive indexes of liquids,
such as, for example, Abbe-type or Pulfrich-type refractometers,
are well known. When using such refractometers, one surface of a
transparent member having a known refractive index is brought into
contact with a solution to be examined a light is directed towards
the surface of the transparent member and its angle of refraction
is measured to determine the refractive index. However, these
refractometers are not entirely satisfactory since the steps for
their use are complicated, involving collecting a fixed amount of
the solution to be examined, maintaining the solution stationary
and calculating the index. In addition, when the refractive index
of the solution varies with time or is converted to an electric
signal which is detected by remote control, accurate measurement of
the index can be very difficult.
Another known apparatus for measuring the density of liquids by
determining the refractive index is disclosed in U.S. Pat. No.
3,977,790 to Schweizer et al. The apparatus utilizes a divergent
light ray radiated from a light source into a light-conductive rod,
the light ray being non-parallel with the longitudinal axis of the
light-conductive rod. When the divergent ray reaches a measuring or
incident surface of the rod, the light ray is diffused so as to
utilize the total reflection angle on the measuring surface.
Therefore, the fact that the light ray is non-parallel with the
axis of the rod is advantageous since the light ray can be applied
to the measuring surface in a wide range.
An object of the present invention is to eliminate the
above-mentioned problems with conventional refractometers.
Another object of the present invention is to provide an optical
instrument wherein an accurate measurement of the specific gravity
of a solution can be obtained by a relatively easy operation.
Yet another object of the present invention is to provide an
optical instrument which is simple in structure and low in
cost.
A further object of the present invention is to provide an optical
instrument adaptable to a variety of uses.
SUMMARY OF THE INVENTION
In its broader aspects, the present invention comprehends an
optical instrument for measuring the specific gravity of a solution
which comprises an elongated transparent member, a photosensitive
element and a light emitting element located at one end of the
transparent member to respectively receive or send light through
the transparent member, an incident light surface located at the
opposite end of the transparent member and oriented so as to be
inclined with respect to the incident rays of light directed
thereagainst from the light-emitting element, and a reflector
surface located adjacent to the incident light surface and oriented
so as to be capable of reflecting the reflected light from the
incident light surface to the photosensitive element in parallel
with the light emitted from the light source. In operation the
optical instrument is immersed in the solution whose specific
gravity is to be measured such that the external surface of the
incident light surface is in contact with the solution, the light
incident thereon being divided into a light portion which enters
the solution and a light portion which is reflected towards the
reflector surface, this reflected light being then 100% reflected
towards the photosensitive element to allow for a determination of
the specific graivty of the solution from the received light
flux.
The present invention will be more easily understood by referring
to the following drawings and description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B show explanatory views of embodiments of optical
instruments according to the present invention,
FIG. 2 shows a drawing which explains the principle of the optical
instrument of the present invention,
FIG. 3 shows interrelation curves of incident light angles,
reflected light fluxes and specific gravities of sulfuric acid,
FIG. 4 depicts the measuring principle of a conventional optical
instrument, i.e., as described in U.S. Pat. No. 3,977,790 to
Schweizer et al,
FIG. 5 shows a further embodiment of optical instrument according
to the present invention,
FIG. 6 depicts another embodiment of optical instrument according
to the present invention, and
FIG. 7 shows a still further embodiment of optical instrument
according to the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In FIG. 1A, which shows a first embodiment of optical instrument
according to the present invention, the instrument body consists of
a transparent glass member 1 and an elongated base part 2 made of a
synthetic resin, the glass member 1 having an incident light
interface 1a and a reflective interface 1b at the tip which
together enclose an angle of about 90 degrees, a mirror 3 being
fitted to the reflective interface 1b so as to reflect 100% of the
light striking its surface. The incident light interface 1a and the
reflective interface 1b each have flat surfaces. The mirror 3 is
formed by securing a film of, e.g., aluminum, silver or gold to the
glass member by vapor deposition. A light source 4 consisting of a
light-emitting diode or the like is located in the upper portion of
the elongated base part 2 so as to emit, when activated by electric
power fed from an electric power source (not illustrated), light
towards incident light interface 1a. Further, a photosensitive
element 5 consisting of a phototransistor is arranged in parallel
with the light source 4 in the upper portion of the base part 2.
Light from the light source 4 may be partly reflected by the
incident light interface 1a and may reach the reflective interface
1b, and further the light reflected by this interface 1b may be
directed in parallel with the light directed toward the incident
light interface 1a. Also, it is a requirement that the light should
have as little expansion as possible so that an accurate
measurement may be possible. In the drawing, a first through-hole 6
in the base part 2 provides a passageway for the light from the
light source 4 to pass towards interface 1a, and a second through
hole 7 provides a passageway for the reflected light from interface
1b to pass towards the photosensitive element 5. A paralleling lens
8 for reducing expansion in the light emitted from the light source
4 is located in the through-hole 6. A protective material 9
surrounds the base part 2 for preventing solution from entering the
glass member 1 at its point of connection with the base part 2.
In FIG. 1B, which shows another embodiment of the present
invention, a tubular light-limiting limiting path member 10 is
located in the through-hole 6 on the light source 4 side which is
made of a non-transparent material as, for example, a synthetic
resin or ceramic. This member 10 has a diameter somewhat smaller
than that of the through-hole 6 and it includes a fine hole along
its axis.
In operation, either of the instruments shown in FIGS. 1A or 1B are
about half dipped in a solution 11 to be examined. The light L
radiated from the light source 4 will pass through the transparent
member to reach the incident light interface 1a at an incident
light angle i and will be divided. One divided light portion
L.sub.1 will be incident upon the solution 11 to be examined. The
other divided light portion L.sub.2 will be internally reflected
within the transparent member 1. Further, the light L.sub.3
reflected by the reflector 3 will be directed back to the
photosensitive element 5. In case the incident light angle is close
to 90 degree, the light flux of the reflected light portion L.sub.2
will be represented by the following formula by the law of general
light reflection: ##EQU1## wherein
K is a constant determined by the incident angle i,
L.sub.V is a total light flux radiated from the light source,
n.sub.A is a refractive index of the transparent member and
n.sub.B is a refractive index of the solution to be examined.
FIG. 2 can be used to explain the general principle of the present
invention. When a light L.sub.O having an energy E.sub.O is
projected at an incident light angle i upon an interface C with a
substance B having an optical refractive index n.sub.B through a
substance A having an optical refractive index n.sub.A, the light
L.sub.O will be divided into a reflected light portion L.sub.1
having a reflection angle i and a refracted light portion L.sub.2
having a refraction angle r. As a result of theoretical
considerations, it is found that if the respective energies are
E.sub.1 and E.sub.2, the relation of the following formulas will be
established: ##EQU2##
By the above formulas, if i is constant, E.sub.1 will vary with
only the refraction angle r by the substance B. Theoretically this
means that the refractive index of the substance B can be found by
measuring the energy E.sub.2 at a photosensitive point at which a
non-divergent straight-lined finely throttled beam-shaped light is
arranged symmetrically with the normal.
Now, in case an optical glass of a refractive index of 1.512 is
used for the transparent member and sulfuric acid solution having
differing specific gravities is used for the solution to be
examined, the incident light angle based on the critical angle
calculation will be as follows:
TABLE 1 ______________________________________ Curve A B C C
______________________________________ Incident light 61.60.degree.
63.32.degree. 64.71.degree. 65.96.degree. angle i Specific gravity
value 1.000 1.100 1.200 1.300 of sulfuric acid Refractive index
1.333 1.351 1.367 1.381 ______________________________________
In the curves A, B, C and D, the incident light angle i is so
determined that a total reflection may be made at each of the
specific gravity values of 1.000, 1.100, 1.200 and 1.300.
One curve A will now be described in detail. When an optical
instrument of the present invention in which the incident light
angle i has an incident light interface of 61.60 degrees is used,
if various measurements are made by varying the specific gravity of
the sulfuric acid, at a specific gravity of 1.000 the reflected
light flux will be maximum in the total reflection. If this is
given a value of 100, the reflected light flux will reduce to 25 at
a specific gravity of 1.100 and to 10 at a specific gravity of
1.200. That is to say, with an increase in the specific gravity
value, the reflected light flux will decrease. The curve A in FIG.
3 shows this relation. The curves B, C and D are obtained in the
same manner as curve A and show the same relations.
FIG. 4 is an explanatory view showing the principle of U.S. Pat.
No. 3,977,790 to Schweizer et al. As described above, in the above
U.S. patent a total reflection phenomenon of a light on an
interface is utilized by using a divergent ray. That is to say, a
light coming out of a light source 21 will become a light having an
expansion from L.sub.1 to L.sub.3 when passing through a slit 22,
it will pass through a transparent member A and it will enter an
interface C with a substance B to be measured. There, the light
will become a light having light fluxes of reflected lights
L'.sub.1 and L'.sub.3, which will be received on a photosensitive
surface 23 and will be transmitted as an electric signal. It is
well known that, in such case, the incident light angle i of the
interface C with the normal can be made to make a total reflection
by properly selecting the transparent member A and the optical
refractive indexes n.sub.A and n.sub.B of the substance to be
examined. In such case, the incident light angle is called a total
reflection angle or critical angle and is represented by the
following formula:
where i.sub..theta. is a critical angle and n.sub.A
>n.sub.B.
FIG. 4 shows the manner in which the optical refractive index of
the substance to be examined varies from n.sub.B1 to n.sub.B3 and
thereby the critical angle varies from i.sub..theta.1 to
i.sub..theta.3. In case n.sub.B is of an intermediate value
n.sub.B2, the light between the critical angles i.sub..theta.2 and
i.sub..theta.3 will be reflected by the total reflection but the
other lights than it will be absorbed into the substance B as
refracted lights and will not be projected on the photosensitive
surface 23. The hatched portion means a light flux not projected.
At the time of n.sub.B3, the light flux will be of a minimum value
and, at the time of n.sub.B1, the light flux will show a maximum
value. It is the measuring principle of the above-mentioned U.S.
patent to measure the optical refractive index of n.sub.B by
measuring the width of this projected light flux. Therefore, it is
required that the light projected on the interface should have an
expansion width large enough to cover at least the abovedescribed
critical angle variation range. By the way, as the specific gravity
variation range in a sulfuric acid lead battery is about 1,000 to
1,320, the projected light flux must have a critical angle width of
at least 61 to 66 degrees (as calculated by using the glass member
having a light refractive index of 1.516 as a transparent
member).
In the present invention, in order to elevate the measuring
precision, it is preferable to make the light from the light source
a beam light, that is, a non-divergent straight-lined ray as much
as possible. Thus, the light from a general light-emitting diode
having an expansion width of about 10 degrees is reduced to an
expansion of 0.5 degree by the paralleling lens 8 in FIG. 1A.
Alternately, as shown in FIG. 1B, the expansion component of the
light can be reduced by passing the light for a fixed distance
through a pinhole or a slit extending through the light-emitting
path member 10. The following formula is shown by a passing
distance L and pinhole diameter d of the light-emitting path in
member 10:
In case d/L=0.1, .theta.=5.7.degree..
In case d/L=0.02, .theta.=1.14.
The light passing through such light-limiting path will be
considerably reduced in its expansion.
When experimentally confirmed, in the case of the parallelization
by using a convex lens of a diameter of 5 mm and focal length of 20
mm, the expansion width is reduced to 0.5 degree without reducing
the effective light flux. Further, in the case of a lens of a
diameter of 5 mm and focal length of 12 mm, the expansion width was
0.8 degree. The parallelism was further improved by using
semiconductor laser or gas laser rays for the light source but
there are defects in the size and price. These are all confirmed to
operate without trouble for the measurement of the refractive index
of the sulfuric acid electrolyte. Experimentally it is preferable
that .theta. is not more than 1.5 degrees. If .theta. exceeds 1.5
degrees, the light expansion will become large and the measuring
precision will deteriorate. It is confirmed by experiments that if
.theta. is not more than 1.5 degrees, the decomposability in the
case of measuring the specific gravity will be about 0.002, but at
2.5 degrees it will be .+-.0.005 and at 4 degrees it will increase
to about .+-.0.014. In the case of utilizing a light-limiting path,
L will be 2 to 35 mm and d will be preferably in the
above-mentioned .theta. range. By the way, the refractive index of
the glass member is required to be above 1.5. If it is not above
1.5, the measuring range will become narrow and the precision will
decrease. This requirement is important particular in the
measurement of the specific gravity of the electrolyte of sulfuric
acid battery. The transparent member can be made of not only glass,
but also of a synthetic resin. However, a methacrylic resin will be
attacked by sulfuric acid on the interface, which will influence
the refractive index, and thus such a resin cannot be used. Vinyl
chloride, polycarbonate and polyvinylidene chloride can be used as
transparent materials, these being acid proof and at the same time
displaying the above-mentioned refractive index.
______________________________________ Refractive index
Transparency ______________________________________ Vinyl chloride
1.54 70 to 90% Polycarbonate 1.58 93 to 95% Polyvinylidene chloride
1.60 50 to 70% ______________________________________
FIG. 5 shows another modification of the present invention. It is
positioned particularly into a lead acid battery and is adapted to
measure the specific gravity of the electrolyte or to measure the
charge or discharge of the battery. It is fixedly connected with a
base part 102 made of a synthetic resin or the like. A reflector
103 is provided at the tip 101b of the transparent member 101 in
the same manner as in the device in FIG. 1. A light source 104 and
photosensitive element 105 are arranged in parallel with each other
in the upper portion of the base part 102. The base part is
provided with through-holes 106 and 107. A paralleling lens 108 is
arranged particularly within the through hole 106 on the light
source 104 side. This device body is fitted to an annular sleeve
109 which is screwed into a female screw 112 of the lid of the lead
acid battery with a male screw 110 on the outer periphery of the
annular sleeve 109. In operation, the tip of the transparent member
is dipped in the electrolyte 113 consisting of sulfuric acid of a
required specific gravity. A plate 114 of the lead acid battery is
contained together with the electrolyte 113 in a battery container
115.
Now, a light L radiated from the light source 104 will reach the
first incident light interface 101a and will be divided into a
light portion L.sub.1 entering the electrolyte 113 and a reflected
portion L.sub.2. This light portion L.sub.2 will be reflected by
the reflector 103, will reach the second incident light interface
101a' and will be divided into a light portion L.sub.3 entering the
electrolyte 113 and a reflected light portion L.sub.4. The light
portion L.sub.4 will further reach the photosensitive element 5.
Its light flux is represented by the following formula: ##EQU3##
wherein
i is an incident light angle on the incident light interface of the
light L and
r is a refraction angle in the electrolyte of L.sub.1 and
L.sub.3.
As described above, the light flux of the light portion L.sub.4
reaching the photosensitive element 105 will vary correlatively
with the specific gravity value of the sulfuric acid of the
electrolyte 113.
Now, the relation between the specific gravity value of the
sulfuric acid and the light current shown by the photosensitive
element is as follows:
TABLE 2 ______________________________________ Specific gravity
value of sulfuric 1.100 1.150 1.200 1.250 1.300 acid Light current
(mA) 1.50 1.12 0.80 0.48 0.35
______________________________________
The above-described modification applying the optical instrument of
this embodiment to a lead acid battery has the following further
advantages.
As the incident light interfaces of the transparent member are
plural, the rate of reduction of the light reaching the
photosensitive element will be large. As a result, any minute
variation of the specific gravity of the sulfuric acid can be
detected more easily. As the incident light interfaces are formed
to be sloped, during the use of the lead acid battery, generated
oxygen and hydrogen gases will not be deposited on the sloped
incident light interfaces. As a result, gases will not be deposited
on the incident light interfaces, the light will not be temporarily
disturbed and that the measured value will not be abnormal.
However, as required, i.e., so that no gas may be deposited on the
incident light interface, there may be provided either a shielding
plate between the plates or a cleaning means on the incident light
interface. Further, it is well known that a lead acid battery will
show a perfect discharge when the specific gravity of the sulfuric
acid of the electrolyte is about 1.150 and a perfect charge at
about 1.280. However, by a special using method, it may be expanded
to be about 1.020 at the end of the discharge and about 1.320 at
the end of the charge. In case the optical instrument of the
present invention is thus applied to a lead acid battery, there
will be able to be easily known the specific gravity value of the
sulfuric acid from the above described reflected light flux and the
charge or discharge through it. It is an inherent advantage as
applied to a lead acid battery.
FIG. 6 shows another modification of the present invention. An
optical instrument is shown wherein a transparent member 201 and
base 202 are connected with a light source 204 and photosensitive
element 205 through respective optical fiber cords 209 and 210 made
of glass much to the advantage of remotely measuring a solution.
Its operation will be as follows: A light L radiated from the light
source 204 to the transparent member 201 via a luminous optical
fiber cord 209 and a paralleling tens 208 will be reflected by a
reflector 211, then it will reach an incident light interface 201a
and then it will be divided into a light portion L.sub.1 entering
the solution 211 to be examined and a reflected light portion
L.sub.2 reflected by the incident light interface 201a. The
reflected light portion L.sub.2 will reach the photosensitive
element 205 through the luminous optical fiber cord 210. The light
flux of this reflected light portion L.sub.2 will be displayed by a
meter or digits through an amplifier. Thus the specific gravity of
the electrolyte and the charge or discharge of the lead acid
battery can be remotely measured. As a result, there is an inherent
advantage that the maintenance of the lead acid battery is
easier.
FIG. 7 shows still another modification of the present invention. A
light L coming out of the light source 204 will pass through a
light-limiting path 210 and will be reflected by the reflective
interface 201b of the transparent member 201. On the incident light
interface 201a, a portion of the light L will advance as a light
L.sub.1 into the electrolyte 211 and the other portion L.sub.2 of
the light L will be reflected and, will advance through the
transparent member 201 and will be received by the photosensitive
element 205 in the base part 202. In this modification, the light
from the light source will be reflected by the reflective interface
and then will be applied to the incident light interface.
Therefore, the measurement can be made.
As further another modification, the light-limiting path may be
brought before the photosensitive element. However, in this manner,
the effective light flux will decrease.
It goes without saying that the optical instrument of the present
invention can be used to not only measure the specific gravity of
the acid in a lead acid battery but also to measure the
characteristics of other solutions as well, for example, to
determination the concentration of an aqueous solution of caustic
soda or common salt, a petroleum distillate or a transformer
oil.
Other modifications of the present invention are also possible
without departing from the spirit of the present invention. For
example, though the optical instrument of the present invention can
be constructed so as to be fixed to the lead acid battery, it is
not limited to this construction but instead it can be constructed
as a a portable transparent member to be dipped by hand into an
electrolyte in case it is only necessary to measure the
electrolyte.
Further, it goes without saying that whether the light radiated
from the light source will reach the reflector through the incident
light interface of the transparent member or will reach the
incident light interface through the reflector can be freely
selected and designed.
While the present invention has been described with reference to
particular embodiments thereof, it will be understood that numerous
modifications may be made by those skilled in the art without
actually departing from the spirit and scope of the invention as
defined in the appended claims.
* * * * *